<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>

        let fraction = Number(prompt('请输入你的分数'))
        if(fraction>=90){
            document.write('A')
        } else if(fraction>=80){
            document.write('B')
        } else if(fraction>=70){
            document.write('C')
        } else if(fraction>=60){
            document.write('D')
        } else {
            document.write('E')
        }
    </script>
</body>
</html>